The search for an autoimmune origin of psychotic disorders: Prevalence
of autoantibodies against hippocampus antigens, glutamic acid
decarboxylase and nuclear antigens
Carolin Hoffmann
a,1, Shenghua Zong
a, Marina Mané-Damas
a, Jo Stevens
a,2, Kishore Malyavantham
b,3,
Cem
İsmail Küçükali
c, Erdem Tüzün
c, Marc De Hert
d,e, Nico J.M. van Beveren
f, Emiliano González-Vioque
g,4,
Celso Arango
g, Jan G.M.C. Damoiseaux
h, Bart P. Rutten
a, Peter C. Molenaar
a,
Mario Losen
a, Pilar Martinez-Martinez
a,⁎
a
Department of Psychiatry and Neuropsychology, School for Mental Health and Neuroscience, Maastricht University, Maastricht, the Netherlands
b
IMMCO Diagnostics, Inc., 60 Pineview Drive, Buffalo, NY, USA
cDepartment of Neuroscience, Institute for Experimental Medical Research (DETAE), Istanbul University, Istanbul, Turkey dUPC KU Leuven, KU Leuven Department of Neurosciences, Belgium
e
Antwerp Health Law and Ethics Chair - AHLEC, University Antwerp, Antwerp, Belgium
f
Department of Psychiatry, Erasmus University Medical Center, Rotterdam, the Netherlands
g
Child and Adolescent Psychiatry Department, Hospital General Universitario, Gregorio Marañón, School of Medicine, Universidad Complutense, IiSGM, CIBERSAM, Madrid, Spain
h
Central Diagnostic Laboratory, Maastricht University Medical Center, Maastricht, the Netherlands
a b s t r a c t
a r t i c l e i n f o
Article history: Received 9 June 2020
Received in revised form 12 December 2020 Accepted 30 December 2020 Available online xxxx Keywords: Psychoses Neuroimmunology Autoantibodies
The etiology of psychotic disorders is still unknown, but in a subgroup of patients symptoms might be caused by an autoimmune reaction. In this study, we tested patterns of autoimmune reactivity against potentially novel hippocampal antigens. Serum of a cohort of 621 individuals with psychotic disorders and 257 controls were first tested for reactivity on neuropil of rat brain sections. Brain reactive sera (67 diseased, 27 healthy) were fur-ther tested for antibody binding to glutamic acid decarboxylase (GAD) isotype 65 and 67 by cell-based assay (CBA). A sub-cohort of 199 individuals with psychotic disorders and 152 controls was tested for the prevalence of anti-nuclear antibodies (ANA) on HEp2-substrate as well as for reactivity to double-stranded DNA, ribosomal P (RPP), and cardiolipin (CL). Incubation of rat brain with serum resulted in unidentified hippocampal binding pat-terns in both diseased and control groups. Upon screening with GAD CBA, one of these patpat-terns was identified as GAD65 in one individual with schizophrenia and also in one healthy individual. Two diseased and two healthy individuals had low antibody levels targeting GAD67 by CBA. Antibody reactivity on HEp-2-substrate was in-creased in patients with schizoaffective disorder, but only in 3 patients did antibody testing hint at a possible di-agnosis of systemic lupus erythematosus. Although reactivity of serum to intracellular antigens might be increased in patients with psychotic disorder, no specific targets could be identified. GAD antibodies are very rare and do not seem increased in serum of patients with psychotic disorders.
© 2021 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).
1. Introduction
The etiology of psychotic disorders is still unknown, but in a
sub-group of patients the symptoms might be caused by an autoimmune
reaction (
Hoffmann et al., 2016
). Early suspicions on a link between
autoimmunity and psychotic disorders were invigorated by the
dis-covery of brain reactive immunoglobulins (
Heath and Krupp,
1967
). Also, the increased occurrence of psychosis in autoimmune
disorders and vice versa suggests overlapping etiological factors
(
Benros et al., 2014a
;
Benros et al., 2014b
). A shared risk factor for
both diseases is the prior occurrence of infections (
Benros et al.,
⁎ Corresponding author at: Universiteitssingel 50, Room 1.108, 6229 ER Maastricht, P.O. Box 616, 6200 MD Maastricht, the Netherlands.
E-mail address:p.martinez@maastrichtuniversity.nl(P. Martinez-Martinez).
1
Present address: Centre for Biomedical Research - CBMR, Universidade do Algarve, Portugal.
2Present address: Antibody Development, Centralized and Point of Care Solutions,
Roche Diagnostics, Penzberg, Germany.
3
Present address: Inova Diagnostics, San Diego, United States of America.
4
Present address: Unit of Diagnosis and Treatment of Congenital Metabolic Diseases, Hospital Clínico Universitario de Santiago de Compostela, Health Research Institute of Santiago de Compostela (IDIS), Santiago de Compostela, Spain.
https://doi.org/10.1016/j.schres.2020.12.038
0920-9964/© 2021 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
Contents lists available at
ScienceDirect
Schizophrenia Research
2011
). In addition, a common genetic predisposition was found for
schizophrenia and six immune system-related diseases, including
systemic lupus erythematosus (SLE) (
Pouget et al., 2019
). Recently,
much attention has been drawn to the role of autoantibodies
targeting neuronal surface antigens (NSAbs) in the brain of patients
with autoimmune encephalitis who often present with psychosis.
One of the proteins targeted is the N-methyl-
D-aspartate receptor
(NMDAR) causing patients to develop characteristic neurologic and
psychiatric symptoms (
Dalmau et al., 2011
). It is clinically important
that these diseases respond very well to immunosuppressive
treat-ment indicating that any neuronal damage might be largely
revers-ible (
Graus et al., 2016
;
Varley et al., 2017
;
Zandi et al., 2014
).
Whether NSAbs can occur in purely psychotic patients, however, is
less clear; their prevalence varies between 0 and 11% (
Bergink
et al., 2015
;
Endres et al., 2015
;
Lennox et al., 2017
), possibly due
to differences in the methodology of antibody detection and patient
cohorts (
Jezequel et al., 2017
;
Leypoldt et al., 2017
;
Pathmanandavel
et al., 2015
). In our own studies, autoantibodies against NMDAR and
five other neuronal surface antigens in patients with a broad
diag-nostic spectrum of psychotic disorders were found to be absent
after careful cross-validation to eliminate false positives (
de Witte
et al., 2015
;
Hoffmann et al., 2019
).
In many autoimmune diseases neuropsychiatric problems are
com-mon. Within the group of systemic autoimmune rheumatic diseases
(SARD), especially SLE may have neurological manifestations, the
so-called neuro-lupus (
Damoiseaux et al., 2015
;
Flower et al., 2017
;
Pego-Reigosa and Isenberg, 2008
;
Unterman et al., 2011
). This warrants the
testing for anti-nuclear antibodies (ANA), antibodies to
double-stranded (ds) DNA, anti-extractable nuclear antigens (ENA) (including
Ribosomal P protein (RPP)), and cardiolipin (CL) in patients with
symp-toms of psychosis. For instance, the presence of anti-RPP and anti-ds
DNA cross-reacting to NMDAR subunit 2 have been associated with
in-creased risk of neuropsychiatric symptoms in SLE (
Hanly et al., 2011
;
Ho
et al., 2016
). Antibodies in general have poor or no access to intracellular
antigen targets and are thus unlikely to bind to them and cause a direct
pathogenic effect on the function of neurons. Yet, presence of certain
au-toantibodies might still be indicative for other autoimmune disease
mechanisms (mediated by co-existing autoantibodies or autoreactive
T cells, for example) that can be targeted by immunosuppressive
treat-ment. Autoantibodies against the intracellularly located glutamic acid
decarboxylase (GAD), which is the rate-limiting enzyme in the
synthe-sis of gamma amino-butyric acid (GABA) occur in serum and CSF of
pa-tients with several neurological and endocrine syndromes. All these
syndromes are characterized by dysfunction of the GABAergic
sys-tem (
Alexopoulos and Dalakas, 2013
;
Fouka et al., 2015
;
Saiz et al.,
2008
) suggesting that in this case the autoantibodies are a relevant
biomarker for an autoimmune mechanism targeting this system.
GAD autoantibodies are also a biomarker for diabetes mellitus type
1, but antibodies are reported to occur in lower titers than in
neuro-logical syndromes (
Nakajima et al., 2018
). Notably, some GAD
antibody-positive conditions are responsive to immunosuppressive
treatment, e.g. autoimmune epilepsy, even though to a lesser extent
than patients with NSAbs (
Daif et al., 2018
;
Vinke et al., 2018
). There
is other evidence that intracellular proteins could be autoimmune
targets. In an animal model for the Stiff person syndrome, intrathecal
application of antibodies against amphiphysin, an intracellular
vesic-ular protein, leads to symptoms of reduced GABAergic transmission
(
Geis et al., 2010
).
Here, we further characterize the serum binding patterns on rat
brain of a cohort that tested negative for antibodies against
neuro-nal surface antigens. We extend our antigen speci
fic search for
glutamic acid decarboxylase autoantibodies and tested for the
occurrence of systemic autoimmune rheumatic disease-related
au-toantibodies in patients with psychotic disorders and healthy
indi-viduals including anti-nuclear antibodies (ANA), and antibodies to
dsDNA, RPP and CL.
2. Methods
2.1. Study population
Samples and patient data were collected with written informed
con-sent according to national and institutional ethical guidelines and the
Helsinki Declaration, with additional informed consent by legal
repre-sentatives for patients under age 18. The ability to provide written
in-formed consent was evaluated by a psychiatrist by a face-to-face
interview using a series of open-ended questions evaluating
compre-hension, reasoning, choice making and appreciation skills of the patient.
The study population represents psychotic disorders and covers
poten-tial differences in diagnosis (
Table 1
). This is the same population used
in our earlier study on the occurrence of NSAbs (
Hoffmann et al., 2019
).
The cohorts from Rotterdam and France are part of the European
net-work of national schizophrenia netnet-works studying Gene-Environment
Interactions (EU-GEI,
http://www.eu-gei.eu
).
2.2. Psychiatric diagnosis
The diagnosis was established by the treating psychiatrists based
on the DSM-IV. The group of patients with psychotic disorders
in-cluded schizophrenia, schizoaffective, brief psychotic disorder,
schizophreniform, and other psychotic diagnoses, i.e. psychosis not
otherwise speci
fied, delusional disorder, substance induced
psycho-sis, paranoid, and schizoid personality disorder.
2.3. Rat brain immunohistochemistry
Procedures were approved by the animal experiment committee at
Maastricht University as well as the central committee of animal
experiment (CCD) (WP 2016-005-001). Neuronal autoantibodies were
identi
fied by IHC on rat brain tissue following standard methods
(
Gresa-Arribas et al., 2014
;
Hoffmann et al., 2019
;
Titulaer et al.,
2014
). In brief, Lewis rat brains were
fixed for 1 h in 4%
paraformalde-hyde and cryoprotected in 30% sucrose solution. After blocking with
0.3% H
2O
2and 5% goat serum, sections were incubated with human
serum diluted 1: 200 in 5% goat serum overnight at 4 °C. After
incubat-ing with biotinylated goat anti-human IgG Fc
γ (1:3200, 109–066-008,
Jackson ImmunoResearch) for 2 h at 20 °C, tissue was incubated with
VECTASTAIN Elite ABC kit (Vector lab., # PK 6100) for 1 h at 20 °C and
the reactivity developed using diaminobenzidine. Staining included
serum samples from healthy individuals as negative controls, and
from autoimmune encephalitis patients (against various autoantigens)
as positive controls. Images were taken by the VENTANA iScan HT
slide scanner (20× objective) and observed on the screen (Ventana
Image Viewer). A grade between 0 and 3 was given based on the
inten-sity and contrast of reactivity of sera against the hippocampal neuropil.
All stainings that were scored 1
–3 and inconclusive cases were repeated
and validated by two independent observers of whom at least one was
blinded. Those with inconsistent results were repeated at least once
more and a
final score (1 = borderline, 2 = weak positive, 3 = strong
positive) was given according to all images of one sample.
2.4. Screening anti-GAD autoantibodies with CBA
Speci
fic antibody screening detection was performed using an
in-house CBA for glutamic acid decarboxylase isotypes 65 kDa and 67 kDa
(GAD65, GAD67). The GAD plasmids expressed human GAD65 and
GAD67 with the pCMV6-XL5 plasmid which was a kind gift from Dr.
Francesc Graus (IDIBAPS, Barcelona) (
Arino et al., 2014
). HEK293 cells
were plated on coverslips and transfected with 4
μg expression vectors
of the respective human antigens and expression allowed for 22
–26 h.
Cells were
fixed in 3.6% formaldehyde (#F006, TAAB) for 10 min and
permeabilized with 0.3% Triton-X-100 for 10 min. After blocking with
1% bovine serum albumin (BSA) for 1 h, cells were incubated with
human sera diluted 1:40 in 1% BSA together with an antibody targeting
the respective antigen (rabbit-anti-GAD65 (clone 7309LB, gift from
Chris-tina Hampe, 1:1000); or rabbit-anti-GAD67 (clone 10266/20B, gift from
Christina Hampe, 1:1000)) for 1 h at 20 °C. Reactivity was visualized
after incubation with secondary antibodies goat-anti-human-IgG Fc
γ-Alexa488 (#109-546-170, Jackson, 1:1000) and goat-anti-rabbit
Alexa594 (#111-585-144, Jackson, 1:1000) for 1 h at 20 °C. Screenings
al-ways included a positive control from an autoantibody positive patient
and a negative human serum control. Cover glasses were mounted onto
7
μl DAPI mounting medium (#H-1200, Vector Laboratories) and
evalu-ated by two (of which one blinded) observers independently on the
BX51 Olympus microscope for antibody reactivity. When positive, the
staining was repeated with serial dilution (1,50 up to 1,3200).
2.5. Measuring SARD-related autoantibodies
Screening of SARD-related antibodies was performed in
collabora-tion with IMMCO Diagnostics (Buffalo, New York, USA). Immuno
fluo-rescent analysis (IFA) for ANAs was performed using ImmuGlo
™ANA
HEp-2 kit (#1103, Immco Diagnostics, USA) according to
manufactur-er's instructions. In short, patients' sera were incubated on HEp-2 cells
in a dilution of 1:40 (in serum diluent) to allow binding of antibodies.
Bound antibodies were detected by incubation of the substrate with
fluorescein-labeled, anti-human IgG conjugate provided by the kit.
Re-actions were observed under a
fluorescence microscope (NikonEclipse
50i diagnostic microscope) equipped with appropriate
filters. Enzyme
Linked Immunosorbent Assay (ELISA) or line immune assays (LIAs)
were performed to test for the presence of ENA, dsDNA, CL and RPP
au-toantibodies. To this end an ELISA plate was pre-coated with the
respec-tive antigen(s): ENA (collecrespec-tively detects, in one well, total ENAs against
dsDNA, nDNA, histones, SS-A(Ro), SS-B(La), Sm, Sm/RNP, Scl-70, Jo-1,
and centrometric antigens, ImmuLisa
™ Enhanced ANA Screen ELISA,
catalog # 5175), dsDNA (ImmuLisa
™ Double stranded DNA antibody
Enhanced ELISA, #5120), RPP (IMMULisa Ribosomal P, # 4133), or CL
(ImmuLisa
™ Cardiolipin IgG, IgA and IgM antibody(ACA) Enhanced
ELISAs, #5118G, #5118A and #5118M). Serum was incubated at a
dilu-tion of 1:100. Horseradish peroxidase (HRP) conjugated anti-human
IgG was used for labelling speci
fic antibodies. Enzyme substrate (TMB)
was then added to the wells and the presence of antibodies was
de-tected by a color change produced by the conversion of TMB substrate
to a colored reaction product. The reaction was stopped with H
2SO
4and the intensity of the color change read by a spectrophotometer at
450 nm. Results are expressed in ELISA Units per milliliter (EU/ml)
and reported as positive or negative. Threshold for positivity was >50
for dsDNA and >20 EU/ml for all other antigens.
2.6. Statistics
To test for the difference of rat brain IHC and ANA indirect
immuno-fluorescence scores between the groups, we performed a
non-parametric Kruskal-Wallis test. All tests were done in IBM SPSS Statistics
version 23.0 for Windows.
3. Results
3.1. Novel hippocampal patterns of rat brain IHC are not speci
fic for mental
disorder
In a
first step, we screened 621 patients with psychotic disorders and
257 healthy individuals for the presence of NSAbs. As reported in our
previous publication, we did not identify any sera with antibodies against
NMDAR (GluN1 alone and GluN1/GluN2B), leucine-rich
glioma-inactivated 1 (LGI1),
α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic
acid receptor (AMPAR), or
γ-aminobutyric acid receptor subunit A and B
(GABAaR, GABAbR). One serum sample (from a control participant) had
autoantibodies targeting contactin-associated protein-like 2 (Caspr2) at
a dilution 1:100 in the live version of the CBA. Further, only 2 sera
contained antibodies binding to neurons at a dilution of 1:50; one was
from a patient with schizophrenia and one was from a control participant,
(
Hoffmann et al., 2019
).
Yet, the rat brain IHC revealed some distinct hippocampal patterns,
that we present here. Several sera gave unknown patterns on the
hippocampal neuropil, suggesting that they target novel cell surface or
synaptic antigens. Hippocampal stainings with strong binding (grading
3) could be grouped according to similarity into eight patterns (see
Fig. 1
, Pattern A-H). Two of these samples (indicated with * in
Fig. 1
)
were the sera previously reported to be reactive on live neurons
(
Hoffmann et al., 2019
). Pattern A was prominent and seen with
five
sera (four from patients with schizophrenia and one from a control
in-dividual). This pattern gave a gradient in the dentate gyrus and synaptic
areas of the cornu ammonis (CA). With the same screening strategy for
autoantibodies against neuronal surface and synaptic antigens in
Table 1
Demographic description of cohorts.
Cohort 1 Cohort 2 Cohort 3 Cohort 4 Cohort 5 Cohort 6
Healthy, n 13 – – – 44 200
Psychotic disorders, n
203 23 300 95 – –
Source University Psychiatric Center Catholic University Leuven in Kortenberg
Public services (emergency wards, in-and out- patient clinics) and private clinics in the Paris region (Créteil)
Istanbul University, Aziz Sancar Institute of Experimental Medicine Erasmus Medical Center (EMC) Rotterdam. Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM) Sanquin Maastricht Criteria Patients: DSM-IV diagnosis of schizophrenia, schizoaffective disorder, or bipolar disorder Healthy: No psychiatric antecedents or medication DSM-IV diagnosis of psychotic disorder or mood disorders with psychotic features; substance-induced psychosis were excluded DSM-IV diagnosis of schizophrenia Consecutively admitted patients which initially presented with psychosis, and were finally diagnosed with schizophrenia, as well with a range of other mental disorders Absence of any psychiatric diagnosis according to DSM-IV criteria No presence of a severe medical condition, and no current or past treatment with any antipsychotic drug Blood donors, confirmed to be healthy by general indicators, tested by interviews, hemoglobin and other blood parameters, blood pressure, pulse, and body temperature as well as the absence of infectious diseases Time-span November 2003 to July
2007
June 2010 to May 2014 2011 to 2012. January 2007 to December 2010
March 2014 Reference (De Hert et al., 2006) (Szoke et al., 2014) – (Schwarz et al., 2012) (Pina-Camacho et al.,
2014)
patients with depression and/or anxiety we also found some novel
staining patterns on the hippocampus (
Zong et al., 2020
). Some of
these were overlapping with the here reported reactivity, e.g. the
here reported pattern A has similarity with the pattern C reported
for 4 patients in the study by Zong et al. Interestingly, two samples
resulting in this pattern that had higher antibody titers in that
study also tested positive on live neurons. Further the here reported
pattern C (2 schizophrenia patients, 1 healthy individual) was also
reported for 2 healthy controls labeled as pattern K by Zong et al..
Pattern D (1 schizophrenia patient, 1 control individual) was similar
to that in a previously published staining by
Bergink et al. (2015)
with serum from a patient with post-partum psychosis, which was
also reactive to live neurons.
3.2. Autoantibodies against GAD65 and GAD67 are rare and do not differ
between healthy controls and disease groups
Some of the IHC positive sera might also have autoantibodies
targeting intracellular neuronal antigens. As GAD is an antigen that is
re-lated to neurological syndromes with GABA disturbances, we extended
our antigen-speci
fic screening of all sera that were graded 1–3 and with
CBA testing for GAD65 and GAD67 reactivity. An overview of all the
au-toantibody screening results is shown in
Table 2
. Two sera were found
to be reactive to GAD65 and GAD67; one of a schizophrenia patient
(
Fig. 1
, Pattern F) and one of a healthy participant. We further identi
fied
4 sera reactive to GAD67 alone (at a max. dilution 1:100 or 1:200). Most
GAD67 antibodies cross-react to GAD65 as they bind to a common
epi-tope. This has been observed for antibodies occurring in patients with
diabetes as well as in neurological conditions (
Gresa-Arribas et al.,
2015
;
Jayakrishnan et al., 2011
). However, a case of cerebellar ataxia
presented with antibodies restricted to the GAD67 isotype, indicating
the possibility that there is another type of GAD67 antibodies (
Guasp
et al., 2016
). As there is not enough research on GAD65/67 antibody
re-activity in psychiatric disorders, we prefer not to make the assumption
of cross-reactivity.
Those sera reactive to GAD65 and GAD67 showed hippocampal
re-activity pattern speci
fic to GAD65, which is the same pattern in e.g.
GAD antibody-positive epilepsy (
Niehusmann et al., 2009
). Those sera
reactive to GAD67 alone had each a different hippocampal binding
pat-tern and therefore were considered to contain neuronal autoantibodies
or autoantibodies against unknown antigens (
Fig. 2
). In conclusion, we
identi
fied 2 sera reactive to GAD65 and GAD67 (
Table 3
).
3.3. Serum reactivity to HEp-2 substrate is increased in individuals with
schizoaffective disorder, but speci
fic autoantibodies against dsDNA, RPP,
and CL are not
We investigated the prevalence of SARD-related autoantibodies
in sera of a sub-cohort consisting of 199 patients with psychotic
disorders, and 152 healthy individuals (
Table 2
). The reactivity of
sera to ANAs on HEp-2 cells was increased in individuals with
schizoaffective disordercompared to healthy individuals (Kruskal
Wallis, p = 0.011). However, the number of sera testing positive
for speci
fic antigens (dsDNA, RPP, and CL) here was too low for
rele-vant statistical analysis. We found that 3 sera (2 schizophrenia, 1
schizoaffective disorder) were consistently positive in different
di-agnostic assays (
Table A.1
), so it might be relevant to examine for
clinical signs of SLE in these patients.
Fig. 1. Microscope images from sera positive by rat brain immunohistochemistry (IHC). Hippocampal IHC patterns graded 3 were sorted according to similarity into eight groups. Each image represents reactivity of one serum sample. Each box represents sera with similar hippocampal immunoreactivity patterns. Images labeled with * are from sera that were also reactive on live hippocampal neurons. Pattern F was identified as GAD65 antibody positive.
4. Discussion
In our cohort of patients with psychotic disorders only two samples
were considered positive for GAD autoantibodies; one schizophrenia
pa-tient and one control. This suggests that serum GAD autoantibodies at
high titers are very rare (2 out of 621) in schizophrenia-spectrum
disorders. A previous meta-analysis on the prevalence of GAD
autoanti-bodies in patients with psychosis reported that patients were more likely
to have GAD65 antibodies than controls (odds ratio [OR], 2.24; 95%CI:
1.28
–3.92%; P = 0.005; eight studies; I2 = 0%) with a pooled prevalence
of 5.8% (
Grain et al., 2017
). However, previous studies were using the
more sensitive radio immuno assay (RIA), radio immunoprecipitation
Table 2
Autoantibody screening results.
Controlsa Psychotic
disorders
Schizophrenia Schizoaffective Brief psychotic disorder Schizophreniform Other psychotic diagnoses No. 257 621 476 44 38 47 16 av. age 44.1 34.4 36.6 31.4 26.7 22.9 31.5 % female 47.5 39.9 39.5 61.4 34.2 36.1 18.8 Methods: IHC rat brainb
Tested, no. 257 621 476 44 38 47 16
Grade = 1, no. (%) 14 (5.4) 40 (6.4) 29 (6.1) 4 (9.1) 2 (5.3) 3 (6.4) 2 (12.5) Grade = 2, no. (%) 8 (3.1) 13 (2.1) 10 (2.1) 2 (4.5) 1 (2.6) 0 (0) 0 (0) Grade = 3, no. (%) 5 (1.9) 14 (2.3) 10 (2.1) 1 (2.3) 2 (5.3) 1 (2.2) 0 (0)
CBA (IHC+cohort) Tested, no. 27 67 49 7 5 3 3
Identified antigen 1× GAD65; 2× GAD67 1× GAD65; 2× GAD67 1xGAD65; 1× GAD67 1× GAD67 SARD-related antibodies Tested, no. 152 199 114 40 0 43 2 av. age 41.9 28.4 29.7 31.3 22.3 27.5 % female 49.3 41.2 37.7 57.5 37.2 66.7
ANA IFA Borderline, no. (%) Nucleus 21 (13.8) 18 (9.0) 8 (7.0) 6 (15.0) 3 (7.0) 1 (50.0) Cytoplasm 1 (0.7) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) Positive, no. (%) Nuclear 2 (1.4) 17 (8.5) 10 (8.8) 5 (12.5) 2 (4.7) 0 (0) Cytoplasm 0 (0) 7 (3.5) 4 (3.5) 3 (7.5) 0 (0) 0 (0) ENA ELISA Positive, no. (%) 2 (1.3) 4 (2) 2 (1.8) 2 (5.1) 0 (0)
dsDNA ELISA Positive, no. (%) 1 (0.7) 7 (3.5) 4 (3.5) 3 (7.7) 0 (0) RPP ELISA/LIA Positive, no. (%) 9 (5.9) 7 (3.5) 5 (4.5) 2 (5.1) 0 (0) CL ELISA Positive, no. (%) 12 (7.9) 9 (4.5) 6 (5.5) 2 (5.1) 1 (2.3)
No. (IgA/IgG/IgM) (1/5/0) (3/1/1) (1/1/1) (1/0/0) (1/0/0)
a
Controls consist of 200 blood donors and 57 individuals without psychiatric diagnosis.
b
Data taken fromHoffmann et al. (2019).
Fig. 2. Rat brain immunohistochemistry (IHC) for GAD+ cases. Case 1 shows a typical GAD65+/67+ antibody binding pattern similar to serum from a patient with GAD+ epilepsy. Case 6 shows unknown binding pattern of serum with GAD67 autoantibodies. More details of cases can be found inTable 3.
assay (RIPA), or enzyme-linked immunosorbent assay (ELISA). Therefore,
reported results likely included also the lower antibody titers. From our
unpublished studies, we know that the CBA and IHC detect GAD
antibod-ies of higher titer and we expected higher titers to be more relevant for
autoimmune-related neurological diseases while low titers are usually a
diagnostic marker for diabetes mellitus type 1. A diagnosis of diabetes,
however, was not excluded, which is a confounding factor, especially
be-cause patients with schizophrenia have a higher risk for comorbid
diabe-tes mellitus type 1 (
Benros et al., 2014b
).
None of the patients in our study had a registered diagnosis of SLE,
though we detected autoantibodies to speci
fic SLE related antigens in 3
patients. Further clinical assessment of these patients would be necessary
to determine a possible diagnosis of SLE. SARD-related autoantibodies,
particularly those in SLE, have been associated with the occurrence of
neuropsychiatric symptoms, also referred to as neuropsychiatric lupus
(NPSLE) (
Tay and Mak, 2017
) whereby the most common symptoms
are depression, cognitive dysfunction and anxiety. The reported
preva-lence of psychosis in SLE varies greatly depending on the population
with 2.3% in an English population (
Pego-Reigosa and Isenberg, 2008
),
and up to 11% in a black Caribbean study population (
Flower et al.,
2017
). Little has been reported on the prevalence of SLE in patients with
schizophrenia spectrum disorders. In the overall population of Europe
the prevalence is estimated to be 35/100000 and 110/100000 in
Afro-Caribbean people (
Rees et al., 2017
). In a large Danish National Register
study of 7704 schizophrenia patients, none was reported with a diagnosis
of SLE (
Eaton et al., 2006
). Yet, cases of patients presenting with a
psy-chotic disorder or atypical SLE with predominant psychiatric
manifesta-tions have been described before (
Lungen et al., 2019
;
Mack et al.,
2017
) and raise the question whether atypical presentation of SLE
might hamper the diagnosis in patients presenting with psychotic
disor-ders. In these cases, psychiatric symptoms might represent a prodromal
stage of the disease or a subtype of SLE with isolated CNS involvement.
Marrie et al. found that the incidence of psychiatric comorbidity is
ele-vated in the immune-mediated in
flammatory diseases (IMID) population
(such as in
flammatory bowel disease, multiple sclerosis and rheumatoid
arthritis) as compared with a matched population as early as 5 years
before diagnosis (
Marrie et al., 2019
). Whether this re
flects shared risk
factors for psychiatric disorders and IMID, a shared
final common
inflam-matory pathway or other etiology is still matter of debate.
In the last 10 years, 16 novel autoimmune diseases of the CNS have
been identi
fied, leading to new treatment strategies for neurological
and psychiatric syndromes (
Dalmau et al., 2017
). However, our previous
studies (
de Witte et al., 2015
;
Hoffmann et al., 2019
) indicate that the
prevalence of NSAbs is very low in patients with psychotic disorders
and not different from the prevalence in control populations. It should
be mentioned however, that the percentage of patients with an
autoimmune origin of the disease might still be larger, but the tested
autoimmune antibodies are signs of speci
fic disorders that only affect a
small number of individuals. It was our strategy to select a very
heterogeneous population to represent a wide spectrum of patients.
Treatment-resistant and acute/recent onset patients have been reported
to have a higher prevalence of known autoimmune encephalitis-related
autoantibodies (
Pollak et al., 2019
). Whether this is also the case for
po-tentially novel antigens or SARD-related autoimmunity remains to be
shown.
Our
finding of reactive autoantibodies to rat brain warrants further
re-search for the identi
fication of the antigen as their target. As most of the
sera were not reactive to live neurons, they potentially target intracellular
or glial antigens. Neuronal surface receptors and channels have a high
ho-mology between rat and human so rat tissue can be used for detection of
most human antibodies against these antigens. Some antigens however,
e.g. dopamine receptor 2 are not detected by rat brain IHC. Especially
when considering that novel antigens might be targeted in psychotic
pa-tients, one has to be aware that these might be missed when using the rat
brain IHC. Also, we con
firmed neuronal specificity on primary cultured
life neurons, but we cannot exclude that (i) some neuronal antigens are
expressed at a very low level in the cultured environment, or (ii) some
an-tibodies target other cell types, e.g. microglia or astrocytes. Finally, a
com-bination of serum analysis with cerebrospinal
fluid (CSF) is always
desirable as the presence of intrathecal antibodies increases the likelihood
for disease relevance. Some antibodies, such as anti-NMDAR are better
detectable in CSF, whereas others, such as those targeting LGI-1 and
AQP4 might only be detectable in serum (
Graus et al., 2016
). General
CSF analysis including white blood cell count, oligoclonal bands, and
protein concentration can give further indications of increased intrathecal
in
flammation. CSF and serum analysis in 456 patients with
schizophreniform syndromes also found that established anti-neuronal
IgG antibodies are rare in serum (
Endres et al., 2020
). The study further
reports, that antibodies are even rarer in the CSF but CSF alterations
re-vealed a substantial subgroup with neuroin
flammatory signs.
5. Conclusion
Autoantibodies against nuclear antigens, cardiolipin and GAD are
rare in psychotic disorders. Serum reactivity on brain tissue indicates
antibodies binding to unidenti
fied antigens and future studies should
thus focus on the identi
fication of potentially novel antigens, including
those targeting microglia and astrocytes as well as their disease
rele-vance. The occurrence of SLE-related autoantibodies in 3 patients with
schizophrenia-spectrum disorders warrants further research into the
prevalence of atypical (undiagnosed) SLE in psychiatric disorders as
well as whether psychotic symptoms are increased in the years
preced-ing a diagnosis of SLE. The role of T-cell autoimmunity has not been
ad-dressed in our study but might represent an important pathogenic
mechanism. Additionally, a better characterization of the patient cohort
including neurological and general CSF examination is desirable to
in-crease the chance of identifying individuals with an autoimmune origin
of the disease.
Table 3
Characteristics of patients with positive CBA results.
CBA resulta Conc. Diagnoses Age Sex IHC gradeb
(UM/IDIBAPS)
Correlating patternc Combined conclusiond
Case 1 GAD65/67 1:6400 Schizophrenia 43 f 3/pos. Yes GAD65/67 Case 2 GAD65/67 1:3200 Controle
59 m 2/NA Yes GAD65/67
Case 3 GAD67 1:100 Schizophrenia 31 f 1/neg. No ND
Case 4 GAD67 1:100 Controle 55 f 1/neg. No ND
Case 5 GAD67 1:200 Psychosis NOS 32 m 1/neg. No ND Case 6 GAD67 1:100 Controle
68 m 2/pos. No ND
Conc. = highest still positive serum concentration, UM = Maastricht University, IDIBAPS = Institut d'investigacions Biomèdiques August Pi i Sunyer, ND = not determined.
a CBA for GAD was performed onfixed cells. b
IHC at UM was graded 0–3 and at IDIBAPS positive/negative.
c
Indicates whether the IHC hippocampal pattern resembled the typical pattern of the antigen identified by CBA.
d
A conclusion was drawn based on the combination of different methods. Only, if a sera was tested positive by CBA and the IHC pattern correlated with the CBA results, it was con-sidered positive.
e
Role of the funding source
The funding sources were not involved in study design; in the collection, analysis or interpretation of data; in the writing of the report; or in the decision to submit the article for publication.
Declaration of competing interest None.
Acknowledgement
This work was supported by the Netherlands Organization for Scientific Research (NWO)“Graduate School of Translational Neuroscience Program” (022005019); the Brain Foundation of the Netherlands (KS2012(1)-157); the ZonMW NWO Program
Translationeel onderzoek (40-41200-98-9257); the China Scholarship Council (201507720015); the EU-GEI European Community's Seventh Framework Program (HEALTH-F2-2010-241909, Project EU-GEI); the research fund of the University of Is-tanbul (23979), the Spanish Ministry of Science and Innovation, Instituto de Salud Carlos III (SAM16PE07CP1, PI16/02012, PI19/024); ERDF Funds from the European Commission,“A way of making Europe”, CIBERSAM, Madrid Regional Government (B2017/BMD-3740 AGES-CM-2); European Union Structural Funds; Fundación Familia Alonso; and Fundación Alicia Koplowitz. We would like to thank Dr. Szoke and Dr. Leboyer who provided the samples from the CIBERSAM cohort. We further thank Mr. Ramsperger and Dr. Suresh for testing of the samples at IMMCO Diagnos-tics, Prof. Graus for generous gifts of plasmid DNA for antigen expression and Dr. Hampe for kindly sharing the GAD antibodies with us.
Appendix A
Table A.1
Three cases with comorbid anti-nuclear autoantibodies specific to systemic lupus erythematosus.
Diagnose Age Sex Illness duration (yrs.) ELISA
ANA IFA ANA dsDNA RPP CL
Schizophrenia (paranoid type) 39 Male 0.5 + + − + + (IgG)
Schizoaffective disorder 23 Female 8 + + + − +
Schizophrenia (paranoid type) 21 Female 4.9 + − − + + (IgA) ELISA = enzyme-linked immunosorbent assay, RPP = ribosomal protein P, dsDNA = double-stranded deoxyribonucleic acid, ANA = anti-nuclear antibodies, CL = cardiolipin, ANA IFA = immunofluorescence on HEp-2 substrate for detection of antinuclear antibodies.
References
Alexopoulos, H., Dalakas, M.C., 2013.Immunology of stiff person syndrome and other GAD-associated neurological disorders. Expert. Rev. Clin. Immunol. 9 (11), 1043–1053.
Arino, H., Gresa-Arribas, N., Blanco, Y., Martinez-Hernandez, E., Sabater, L., Petit-Pedrol, M., Rouco, I., Bataller, L., Dalmau, J.O., Saiz, A., Graus, F., 2014.Cerebellar ataxia and glutamic acid decarboxylase antibodies: immunologic profile and long-term effect of immunotherapy. JAMA Neurol 71 (8), 1009–1016.
Benros, M.E., Nielsen, P.R., Nordentoft, M., Eaton, W.W., Dalton, S.O., Mortensen, P.B., 2011.Autoimmune diseases and severe infections as risk factors for schizophrenia: a 30-year population-based register study. Am. J. Psychiatry 168 (12), 1303–1310.
Benros, M.E., Eaton, W.W., Mortensen, P.B., 2014a.The epidemiologic evidence linking au-toimmune diseases and psychosis. Biol. Psychiatry 75 (4), 300–306.
Benros, M.E., Pedersen, M.G., Rasmussen, H., Eaton, W.W., Nordentoft, M., Mortensen, P.B., 2014b.A nationwide study on the risk of autoimmune diseases in individuals with a personal or a family history of schizophrenia and related psychosis. Am. J. Psychiatry 171 (2), 218–226.
Bergink, V., Armangue, T., Titulaer, M.J., Markx, S., Dalmau, J., Kushner, S.A., 2015. Autoim-mune encephalitis in postpartum psychosis. Am. J. Psychiatry 172 (9), 901–908.
Daif, A., Lukas, R.V., Issa, N.P., Javed, A., VanHaerents, S., Reder, A.T., Tao, J.X., Warnke, P., Rose, S., Towle, V.L., Wu, S., 2018.Antiglutamic acid decarboxylase 65 (GAD65) antibody-associated epilepsy. Epilepsy Behav. 80, 331–336.
Dalmau, J., Lancaster, E., Martinez-Hernandez, E., Rosenfeld, M.R., Balice-Gordon, R., 2011.
Clinical experience and laboratory investigations in patients with anti-NMDAR en-cephalitis. The Lancet. Neurology 10 (1), 63–74.
Dalmau, J., Geis, C., Graus, F., 2017.Autoantibodies to synaptic receptors and neuronal cell surface proteins in autoimmune diseases of the central nervous system. Physiol. Rev. 97 (2), 839–887.
Damoiseaux, J., Andrade, L.E., Fritzler, M.J., Shoenfeld, Y., 2015.Autoantibodies 2015: from diagnostic biomarkers toward prediction, prognosis and prevention. Autoimmun. Rev. 14 (6), 555–563.
De Hert, M.A., van Winkel, R., Van Eyck, D., Hanssens, L., Wampers, M., Scheen, A., Peuskens, J., 2006.Prevalence of the metabolic syndrome in patients with schizo-phrenia treated with antipsychotic medication. Schizophr. Res. 83 (1), 87–93.
de Witte, L.D., Hoffmann, C., van Mierlo, H.C., Titulaer, M.J., Kahn, R.S., Martinez-Martinez, P., Disorders, E.C.o.A.M., 2015.Absence of N-methyl-D-aspartate receptor IgG autoan-tibodies in schizophrenia: the importance of cross-validation studies. JAMA Psychia-try 72 (7), 731–733.
Eaton, W.W., Byrne, M., Ewald, H., Mors, O., Chen, C.Y., Agerbo, E., Mortensen, P.B., 2006.
Association of schizophrenia and autoimmune diseases: linkage of Danish national registers. Am. J. Psychiatry 163 (3), 521–528.
Endres, D., Perlov, E., Baumgartner, A., Hottenrott, T., Dersch, R., Stich, O., Tebartz van Elst, L., 2015.Immunologicalfindings in psychotic syndromes: a tertiary care hospital’s CSF sample of 180 patients. Front. Hum. Neurosci. 9, 476.
Endres, D., Meixensberger, S., Dersch, R., Feige, B., Stich, O., Venhoff, N., Matysik, M., Maier, S.J., Michel, M., Runge, K., Nickel, K., Urbach, H., Domschke, K., Pruss, H., Tebartz van Elst, L., 2020.Cerebrospinalfluid, antineuronal autoantibody, EEG, and MRI findings
from 992 patients with schizophreniform and affective psychosis. Transl. Psychiatry 10 (1), 279.
Flower, C., Hambleton, I., Corbin, D., Marquez, S., Edghill, R., 2017.The spectrum of neuro-psychiatric lupus in a Black Caribbean population: a report of the Barbados National Lupus Registry. Lupus 26 (10), 1034–1041.
Fouka, P., Alexopoulos, H., Akrivou, S., Trohatou, O., Politis, P.K., Dalakas, M.C., 2015.
GAD65 epitope mapping and search for novel autoantibodies in GAD-associated neu-rological disorders. J. Neuroimmunol. 281, 73–77.
Geis, C., Weishaupt, A., Hallermann, S., Grunewald, B., Wessig, C., Wultsch, T., Reif, A., Byts, N., Beck, M., Jablonka, S., Boettger, M.K., Uceyler, N., Fouquet, W., Gerlach, M., Meinck, H.M., Siren, A.L., Sigrist, S.J., Toyka, K.V., Heckmann, M., Sommer, C., 2010.Stiff person syndrome-associated autoantibodies to amphiphysin mediate reduced GABAergic in-hibition. Brain 133 (11), 3166–3180.
Grain, R., Lally, J., Stubbs, B., Malik, S., LeMince, A., Nicholson, T.R., Murray, R.M., Gaughran, F., 2017.Autoantibodies against voltage-gated potassium channel and glutamic acid decarboxylase in psychosis: a systematic review, meta-analysis, and case series. Psy-chiatry Clin. Neurosci. 71 (10), 678–689.
Graus, F., Titulaer, M.J., Balu, R., Benseler, S., Bien, C.G., Cellucci, T., Cortese, I., Dale, R.C., Gelfand, J.M., Geschwind, M., Glaser, C.A., Honnorat, J., Hoftberger, R., Iizuka, T., Irani, S.R., Lancaster, E., Leypoldt, F., Pruss, H., Rae-Grant, A., Reindl, M., Rosenfeld, M.R., Rostasy, K., Saiz, A., Venkatesan, A., Vincent, A., Wandinger, K.P., Waters, P., Dalmau, J., 2016.A clinical approach to diagnosis of autoimmune encephalitis. Lancet Neurol. 15 (4), 391–404.
Gresa-Arribas, N., Titulaer, M.J., Torrents, A., Aguilar, E., McCracken, L., Leypoldt, F., Gleichman, A.J., Balice-Gordon, R., Rosenfeld, M.R., Lynch, D., Graus, F., Dalmau, J., 2014.Antibody titres at diagnosis and during follow-up of anti-NMDA receptor en-cephalitis: a retrospective study. Lancet Neurol. 13 (2), 167–177.
Gresa-Arribas, N., Arino, H., Martinez-Hernandez, E., Petit-Pedrol, M., Sabater, L., Saiz, A., Dalmau, J., Graus, F., 2015.Antibodies to inhibitory synaptic proteins in neurological syndromes associated with glutamic acid decarboxylase autoimmunity. PLoS One 10 (3), e0121364.
Guasp, M., Sola-Valls, N., Martinez-Hernandez, E., Gil, M.P., Gonzalez, C., Brieva, L., Saiz, A., Dalmau, J., Graus, F., Arino, H., 2016.Cerebellar ataxia and autoantibodies restricted to glutamic acid decarboxylase 67 (GAD67). J. Neuroimmunol. 300, 15–17.
Hanly, J.G., Urowitz, M.B., Su, L., Bae, S.C., Gordon, C., Clarke, A., Bernatsky, S., Vasudevan, A., Isenberg, D., Rahman, A., Wallace, D.J., Fortin, P.R., Gladman, D., Romero-Diaz, J., Sanchez-Guerrero, J., Dooley, M.A., Bruce, I., Steinsson, K., Khamashta, M., Manzi, S., Ramsey-Goldman, R., Sturfelt, G., Nived, O., van Vollenhoven, R., Ramos-Casals, M., Aranow, C., Mackay, M., Kalunian, K., Alarcon, G.S., Fessler, B.J., Ruiz-Irastorza, G., Petri, M., Lim, S., Kamen, D., Peschken, C., Farewell, V., Thompson, K., Theriault, C., Merrill, J.T., 2011.Autoantibodies as biomarkers for the prediction of neuropsychiat-ric events in systemic lupus erythematosus. Ann. Rheum. Dis. 70 (10), 1726–1732.
Heath, R.G., Krupp, I.M., 1967.Schizophrenia as an immunologic disorder. I. Demonstra-tion of antibrain globulins byfluorescent antibody techniques. Arch Gen Psychiatry 16 (1), 1–9.
Ho, R.C., Thiaghu, C., Ong, H., Lu, Y., Ho, C.S., Tam, W.W., Zhang, M.W., 2016.A meta-analysis of serum and cerebrospinalfluid autoantibodies in neuropsychiatric sys-temic lupus erythematosus. Autoimmun. Rev. 15 (2), 124–138.
Hoffmann, C., Zong, S., Mane-Damas, M., Molenaar, P., Losen, M., Martinez-Martinez, P., 2016.Autoantibodies in neuropsychiatric disorders. Antibodies (Basel) 5 (2), 9–37.
Hoffmann, C., Zong, S., Mane-Damas, M., Molenaar, P.C., Losen, M., Titulaer, M.J., Martinez-Martinez, P., European Consortium of Autoimmune Mental, D, 2019.Absence of auto-antibodies against neuronal surface antigens in sera of patients with psychotic disor-ders. JAMA Psychiatry.
Jayakrishnan, B., Hoke, D.E., Langendorf, C.G., Buckle, A.M., Rowley, M.J., 2011.An analysis of the cross-reactivity of autoantibodies to GAD65 and GAD67 in diabetes. PLoS One 6 (4), e18411.
Jezequel, J., Rogemond, V., Pollak, T., Lepleux, M., Jacobson, L., Grea, H., Iyegbe, C., Kahn, R., McGuire, P., Vincent, A., Honnorat, J., Leboyer, M., Groc, L., 2017.Cell- and single molecule-based methods to detect anti-N-methyl-D-aspartate receptor autoanti-bodies in patients withfirst-episode psychosis from the OPTiMiSE project. Biol. Psy-chiatry 82 (10), 766–772.
Lennox, B.R., Palmer-Cooper, E.C., Pollak, T., Hainsworth, J., Marks, J., Jacobson, L., Lang, B., Fox, H., Ferry, B., Scoriels, L., Crowley, H., Jones, P.B., Harrison, P.J., Vincent, A., 2017.
Prevalence and clinical characteristics of serum neuronal cell surface antibodies in first-episode psychosis: a case-control study. Lancet Psychiatry 4 (1), 42–48.
Leypoldt, F., de Witte, L., Lancaster, E., Titulaer, M.J., 2017.Serum neuronal cell-surface an-tibodies infirst-episode psychosis. Lancet Psychiatry 4 (3), 186–187.
Lungen, E.M., Maier, V., Venhoff, N., Salzer, U., Dersch, R., Berger, B., Riering, A.N., Nickel, K., Fiebich, B.L., Suss, P., Maier, S.J., Egger, K., Tebartz van Elst, L., Endres, D., 2019. Sys-temic lupus erythematosus with isolated psychiatric symptoms and antinuclear anti-body detection in the cerebrospinalfluid. Front Psychiatry 10, 226.
Mack, A., Pfeiffer, C., Schneider, E.M., Bechter, K., 2017.Schizophrenia or atypical lupus er-ythematosus with predominant psychiatric manifestations over 25 years: case anal-ysis and review. Front Psychiatry 8, 131.
Marrie, R.A., Walld, R., Bolton, J.M., Sareen, J., Walker, J.R., Patten, S.B., Singer, A., Lix, L.M., Hitchon, C.A., El-Gabalawy, R., Katz, A., Fisk, J.D., Bernstein, C.N., Burden, C.T.i.D.t, Managing the Effects of Psychiatric Comorbidity in Chronic Immunoinflammatory, D, 2019.Rising incidence of psychiatric disorders before diagnosis of immune-mediated inflammatory disease. Epidemiol Psychiatr Sci 28 (3), 333–342.
Nakajima, H., Nakamura, Y., Inaba, Y., Tsutsumi, C., Unoda, K., Hosokawa, T., Kimura, F., Hanafusa, T., Date, M., Kitaoka, H., 2018.Neurologic disorders associated with anti-glutamic acid decarboxylase antibodies: a comparison of anti-GAD antibody titers and time-dependent changes between neurologic disease and type I diabetes mellitus. J. Neuroimmunol. 317, 84–89.
Niehusmann, P., Dalmau, J., Rudlowski, C., Vincent, A., Elger, C.E., Rossi, J.E., Bien, C.G., 2009.Diagnostic value of N-methyl-D-aspartate receptor antibodies in women with new-onset epilepsy. Arch. Neurol. 66 (4), 458–464.
Pathmanandavel, K., Starling, J., Merheb, V., Ramanathan, S., Sinmaz, N., Dale, R.C., Brilot, F., 2015.Antibodies to surface dopamine-2 receptor and N-methyl-D-aspartate re-ceptor in thefirst episode of acute psychosis in children. Biol. Psychiatry 77 (6), 537–547.
Pego-Reigosa, J.M., Isenberg, D.A., 2008.Psychosis due to systemic lupus erythematosus: characteristics and long-term outcome of this rare manifestation of the disease. Rheumatology (Oxford) 47 (10), 1498–1502.
Pina-Camacho, L., Diaz-Caneja, C.M., Saiz, P.A., Bobes, J., Corripio, I., Grasa, E., Rodriguez-Jimenez, R., Fernandez, M., Sanjuan, J., Garcia-Lopez, A., Tapia-Casellas, C., Alvarez-Blazquez, M., Fraguas, D., Mitjans, M., Arias, B., Arango, C., 2014.Pharmacogenetic study of second-generation antipsychotic long-term treatment metabolic side effects (the SLiM Study): rationale, objectives, design and sample description. Rev Psiquiatr Salud Ment 7 (4), 166–178.
Pollak, T.A., Lennox, B.R., Muller, S., Benros, M.E., Pruss, H., Tebartz van Elst, L., Klein, H., Steiner, J., Frodl, T., Bogerts, B., Tian, L., Groc, L., Hasan, A., Baune, B.T., Endres, D., Haroon, E., Yolken, R., Benedetti, F., Halaris, A., Meyer, J.H., Stassen, H., Leboyer, M., Fuchs, D., Otto, M., Brown, D.A., Vincent, A., Najjar, S., Bechter, K., 2019.Autoimmune psychosis: an international consensus on an approach to the diagnosis and management of psychosis of suspected autoimmune origin. Lancet Psychiatry 7 (1), 93–108.
Pouget, J.G., Schizophrenia Working Group of the Psychiatric Genomics, C, Han, B., Wu, Y., Mignot, E., Ollila, H.M., Barker, J., Spain, S., Dand, N., Trembath, R., Martin, J., Mayes, M.D., Bossini-Castillo, L., Lopez-Isac, E., Jin, Y., Santorico, S.A., Spritz, R.A., Hakonarson, H., Polychronakos, C., Raychaudhuri, S., Knight, J., 2019.Cross-disorder analysis of schizophrenia and 19 immune-mediated diseases identifies shared genetic risk. Hum. Mol. Genet. 28 (20), 3498–3513.
Rees, F., Doherty, M., Grainge, M.J., Lanyon, P., Zhang, W., 2017.The worldwide incidence and prevalence of systemic lupus erythematosus: a systematic review of epidemio-logical studies. Rheumatology (Oxford) 56 (11), 1945–1961.
Saiz, A., Blanco, Y., Sabater, L., Gonzalez, F., Bataller, L., Casamitjana, R., Ramio-Torrenta, L., Graus, F., 2008.Spectrum of neurological syndromes associated with glutamic acid decarboxylase antibodies: diagnostic clues for this association. Brain 131 (Pt 10), 2553–2563.
Schwarz, E., Guest, P.C., Rahmoune, H., Harris, L.W., Wang, L., Leweke, F.M., Rothermundt, M., Bogerts, B., Koethe, D., Kranaster, L., Ohrmann, P., Suslow, T., McAllister, G., Spain, M., Barnes, A., van Beveren, N.J., Baron-Cohen, S., Steiner, J., Torrey, F.E., Yolken, R.H., Bahn, S., 2012.Identification of a biological signature for schizophrenia in serum. Mol. Psychiatry 17 (5), 494–502.
Szoke, A., Charpeaud, T., Galliot, A.M., Vilain, J., Richard, J.R., Leboyer, M., Llorca, P.M., Schurhoff, F., 2014.Rural-urban variation in incidence of psychosis in France: a pro-spective epidemiologic study in two contrasted catchment areas. BMC Psychiatry 14, 78.
Tay, S.H., Mak, A., 2017.Diagnosing and attributing neuropsychiatric events to systemic lupus erythematosus: time to untie the Gordian knot? Rheumatology (Oxford) 56 (suppl_1), i14–i23.
Titulaer, M.J., Hoftberger, R., Iizuka, T., Leypoldt, F., McCracken, L., Cellucci, T., Benson, L.A., Shu, H., Irioka, T., Hirano, M., Singh, G., Cobo Calvo, A., Kaida, K., Morales, P.S., Wirtz, P.W., Yamamoto, T., Reindl, M., Rosenfeld, M.R., Graus, F., Saiz, A., Dalmau, J., 2014.
Overlapping demyelinating syndromes and anti-N-methyl-D-aspartate receptor en-cephalitis. Ann. Neurol. 75 (3), 411–428.
Unterman, A., Nolte, J.E., Boaz, M., Abady, M., Shoenfeld, Y., Zandman-Goddard, G., 2011.
Neuropsychiatric syndromes in systemic lupus erythematosus: a meta-analysis. Semin. Arthritis Rheum. 41 (1), 1–11.
Varley, J., Taylor, J., Irani, S.R., 2017.Autoantibody-mediated diseases of the CNS: struc-ture, dysfunction and therapy. Neuropharmacology. 132, 71–82.
Vinke, A.M., Schaper, F., Vlooswijk, M.C.G., Nicolai, J., Majoie, M., Martinez Martinez, P., Hoffmann, C., Damoiseaux, J., Rouhl, R.P.W., 2018.Anti-GAD antibodies in a cohort of neuropsychiatric patients. Epilepsy Behav. 82, 25–28.
Zandi, M.S., Deakin, J.B., Morris, K., Buckley, C., Jacobson, L., Scoriels, L., Cox, A.L., Coles, A.J., Jones, P.B., Vincent, A., Lennox, B.R., 2014.Immunotherapy for patients with acute psychosis and serum N-methyl D-aspartate receptor (NMDAR) antibodies: a descrip-tion of a treated case series. Schizophr. Res. 160 (1–3), 193–195.
Zong, S., Correia-Hoffmann, C., Mane-Damas, M., Kappelmann, N., Molenaar, P.C., van Grootheest, G., Penninx, B., Rouhl, R.P.W., Losen, M., Martinez-Martinez, P., 2020.
Novel neuronal surface autoantibodies in plasma of patients with depression and anxiety. Transl. Psychiatry 10 (1), 404.
Carolin Hoffmann performed her PhD at Maastricht Univer-sity, where she set-up the research line of autoantibodies in psychotic disorders under supervision of Prof. Pilar Martinez. Since receiving her PhD degree in 2018, she continues her re-search line in Maastricht as a PostDoc. In 2019 she stayed 3 months in the Neuroscience department of Biodonostia (San Sebastian, Spain). She recently received a 6-year fellow-ship from the Portuguese Foundation for Science and Tech-nology (FCT) to work on the role of complement in schizophrenia. In the end of 2020, she joins the Molecular Neuroscience and Gene Therapy Group at the Center for Bio-medical Research in Faro (Portugal).
Shenghua Zong received a Master degree on clinical medi-cine in 2012 from the Zhengzhou University. He was licensed as a medical doctor and worked one year as a resident (on the training to become a neurosurgeon) in Nanjing Benq hospital, China. In October 2014, he came to Prof. Pilar Martinez's lab, Maastricht University and worked as a re-search assistant. From 2015 till 2019, he performed his PhD study on the project of detecting neuronal autoantibodies in neuropsychiatric disorders at Maastricht University sup-ported by a scholarship from China Scholarship Council. Since 2019, he continues his research under the Kootstra Tal-ent Fellowship as a postdoctoral researcher.
Marina Mané-Damas is a PhD-student at the Department of Psychiatry and Psychology at Maastricht University. In 2012 she received her Bachelor degree in Biotechnology at Rovira I Virgili University (Spain) and subsequently performed her Master degree education in Neuroscience at University of Barcelona (Spain) where she graduated in 2013. She worked as a research assistant in Immune receptors of the innate and adaptive system in Institut d-Invertigacions Biomedediques Agust Pi I Sunyer (IDIBAPS). In December 2014 she started her PhD fellowship to study the prevalence and mechanisms of action of autoantibodies of patients with early onset psy-chotic disorders. She is also involved in the study of pathoge-nicity and drug mechanisms in other antibody mediated neuromuscular disorders.
Jo Stevens performed his PhD research 2011–2016 at Maastricht University focusing on Advanced diagnostics and therapeutics for Alzheimer's disease. During this time, he successfully developed a novel PET diagnostic for Alzheimer's disease based on antibodies, investigated effects of immunotherapy in Alzheimer's using antibody engineer-ing techniques, setup a recombinant antibody production technique in an international collaboration, and discovered a novel role of lipid metabolism in an AD mouse model using AAV overexpression. After his graduation, he joined Roche (Munich, Germany) as postdoctoral research involved in an-tibody discovery and generation, where he was promoted to group leader in 2018.
Kishore Malyavantham is currently the Director of Research and Development at Inova Diagnostics, a Werfen Company. Kishore has a Master's degree in Biotechnology and Genetic Engineering from India and a Doctorate in Cell and Molecular Biology from University at Buffalo, New York, USA. Kishore's doctoral research focused on the structure and function of the mammalian cell nucleus and genomic organization. Prior to joining Inova, Kishore served as the Director of R&D at Immco Diagnostics and a Research Assistant Professor at the School of Medicine, University at Buffalo, NY. While at Immco, Kishore lead the development of a new family of multiplex diagnostic assays in line blot format for autoim-mune and infectious disease areas. Kishore also pioneered the development of an FDA cleared HEp-2 substrate com-posed of cells knocked out for DFS70 gene product. Kishore's research has resulted in 30 peer reviewed publications and active patents in varied disciplines. Kishore's current focus is on clinical biomarker discovery as well as development of diagnostic reagents and tech-nologies.
Cemİsmail Küçükali after graduating from the Faculty of Medicine in 1988, he worked as a research assistant in the neurology department of Ghent University, Belgium be-tween 1990 and 1994. He has been working as a lecturer at Istanbul University, Aziz Sancar Experimental Research Insti-tute, Neuroscience Department since 2010. Following his neurology expertise, he completed his master's and doctor-ate in neuroscience. He has received the title of associdoctor-ate pro-fessor in Neurology since 2018. Psychiatric diseases (Psychosis, Depression, Bipolar Affective Disorder and Obses-sive CompulObses-sive Disorder), Neuroimmunology, Animal Modeling, and Neurogenetic researchfields. He has 86 arti-cles and 135 papers in thefield of Psychiatry and Neurosci-ence.
Erdem Tüzün received his medical doctor and neurologist ti-tles in Istanbul University and then worked as a post-doctoral researcher at Oxford, Texas and Pennsylvania Uni-versities. He is currently the chairman of Neuroscience De-partment at Istanbul University. His scientific studies are mainly focused on clinical neuroimmunology.
Marc De Hert is a psychiatrist and psychotherapist at the University Psychiatric Centre (UPC) KU Leuven. He does am-bulatory clinical work in the psychosis care program. He is also a member of the medical council of the UPC KU Leuven. He studied medicine at the University of Antwerp and holds a PhD in biomedical sciences (PhD) from KU Leuven. He is a professor at KU Leuven, in the neuroscience department. Both his clinical expertise and his research area are in the do-main of psychotic disorders. His current research includes: epidemiology, long-term outcomes, physical comorbidity and side effects of antipsychotics, genetic and environmental interactions and psychosocial interventions. He is currently a PhD law student at the University Antwerp.
Nico J.M. van Beveren currently works at Parnnassia Antes Center for Metal Health Care, and is affiliated with the Eras-mus MC, departments of psychiatry and neuroscience. He does research in psychosis His current projects are about finding clinically relevant subgroups of psychotic disorders, focussing on immune and metabolic abnormalities.
Emiliano González-Vioque is at present the Head of Genet-ics Laboratory of the Unit of Diagnosis and Treatment of Con-genital Metabolic Diseases, Hospital Clínico Universitario de Santiago de Compostela, Health Research Institute of Santi-ago de Compostela (IDIS). After his training as specialist in biochemical chemistry in 12 de Octubre Hospital, Madrid, he obtained a Ph.D. in Biochemistry and Molecular Biology at Universidad Autónoma de Madrid School of Medicine fo-cused on mitochondrial disorders. During the next years he continued his research career as a postdoctoral researcher in thefields of mitochondrial disorders in the Vall d'Hebron Research Institute, Barcelona, and molecular basis of neuro-psychiatric diseases in the University of Cambridge (UK) and Gregorio Marañón Research Institute, Madrid.
Dr Celso Arango, MD, PhD, is currently Chair of the Child and Adolescent Department of Psychiatry at Hospital General Universitario Gregorio Marañón, Complutense University in Madrid, Spain, as well as Director of the Gregorio Marañón Psychiatric and Mental Health Institute, Professor of Psychia-try at the Maryland Psychiatric Research Center of the Uni-versity of Maryland in Baltimore, Adjunct Professor of Psychiatry at UCSF in San Francisco, Visiting Professor of Psy-chiatry at Kings College London, and Tenured Full Professor at Complutense University in Madrid. Past President of the ECNP, has served on many executive committees of interna-tional societies and is currently President of the Spanish Psy-chiatry Society since 2019.
Jan G.M.C. Damoiseaux (PhD) is medical immunologist and as such involved in diagnostic testing for immune-mediated diseases. His career has started in basic immunology research and evolved, via research in animal models for autoimmune diseases, towards clinical immunology research. The re-search has been focussed on immune regulation and on au-toantibody testing. He is an active member of the European Autoantibody Standardisation Initiative (EASI) and the Inter-national Consensus on ANA Patterns (ICAP) working party. He has published more than 250 scientific papers in peer-reviewed journals. Many of these papers were the result of close collaboration with renowned national and interna-tional scientists.
Bart Rutten is an internationally renowned academic scien-tist and clinician in translational neuroscience on gene-environment interplay and epigenetics in mental disorders. He graduated as medical doctor withfirst class honours in 2000. During his MD and PhD period, Bart performed re-search at RWTH University in Aachen, the University of Cali-fornia in San Francisico, Emory University (Atlanta), and at Maastricht University, receiving his PhD degree in 2005. Since 2009, he has been active as a certified clinical psychia-trist, combining his clinical activities with teaching, manage-ment and particularly research on translational psychiatry. From 2013– 2017, Bart Rutten has chaired the division of Neuroscience within the school for Mental Health and Neu-roscience, and since 2017 he has become the chair of the de-partment of Psychiatry and Neuropsychology as well as the chair of the clinical department of Psychiatry at MUMC+.
Peter C. Molenaar is senior scientist at the department of Psychiatry and Psychology Division Neuroscience at the School for Mental Health and Neuroscience at Maastricht University. He is trained as a pharmacologist and he has a special interest in diseases with dysfunctional neuronal ion channels (channelopathies). As an associate professor he was formerly heading a neuromuscular research group at the Leiden University Medical Centre.
Mario Losen trained in molecular biology, biochemistry and neuroimmunology. He is an Assistant Professor at the De-partment of Psychiatry and Psychology Division Neurosci-ence at the School for Mental Health and NeurosciNeurosci-ence at Maastricht University. His work has mainly been focused on the development of novel experimental therapies for the treatment of myasthenia gravis, e.g. with recombinant anti-inflammatory IgG4 antibodies, leading to the serendipi-tous discovery of the Fab-arm exchange reaction of human IgG4 in rhesus monkeys. He is PI in the Research Group Ner-vous System Neuroinflammation and Autoimmunity.
Pilar Martinez-Martinez is trained in molecular biology, biochemistry and neuroimmunology. She is Professor of Neuroinflammation in neuropsychiatric disorders at the de-partment of Psychiatry and Psychology Division Neurosci-ence at the School for Mental Health and NeurosciNeurosci-ence at Maastricht University. She is the PI of several European grants examining neuroinflammation with special focus in neurodegenerative diseases and its relationship with the sphingolipid metabolism. Specifically, she has studied CERT and developed the technology to measure and to modulate CERT expression levels. Additionally, she has long lasting ex-pertise in translational neurosciences, and her research focus on understanding the molecular pathogenic mechanisms and uses new therapeutic approaches in animal models with peripheral nervous system and central nervous system disease.
